Speed control for a mixer for providing an incremental power boost

ABSTRACT

A stand mixer having an electrical speed control circuit for providing a temporary incremental power burst to the motor of the mixer.

FIELD OF THE INVENTION

The present invention relates to food mixing apparatus, and inparticular, devices referred to as “stand mixers”, which include a mixerhead placed on a stand to allow hands-free mixing of food items.

BACKGROUND OF THE INVENTION

Stand mixers have been employed for decades to assist in the commercialand domestic preparation of food requiring mixing and/or kneading. Suchstand mixers typically include a base or stand on which a rotatableturntable rests for holding mixing bowls of various sizes. In order tochange from one size mixing bowl to the other, it is generally necessaryto lift the turntable and reposition it in a different hole in the base.This task can be inconvenient, particularly for the elderly who may havedifficulty lifting and/or repositioning the turntable and bowl,particularly if the turntable has become caked with batter or other foodingredients which may tend to cause the turntable to stick to the base.

Stand mixers also typically employ a pair of whippers which are attachedto the front of the mixer and extend downwardly into the bowl containingfood ingredients to be mixed.

While traditional whippers are effective in mixing, there is a tendency,particularly with thick batter or dough, to creep up the center bar thatsupports the whipper blades. This phenomenon, known as “dough creep” canpotentially result in dough being driven up to the mixer head, foulingthe gearing mechanisms, and potentially throwing dough and/or batter outof the bowl.

Prior stand mixers have also commonly used variable speed controlmechanisms, such as dials, knobs, slide levers, etc. While such speedcontrols are effective for incremental speed changes, they do notgenerally provide a “burst” or rapid speed change which is frequentlydesirable to break up large clumps for a short period of mixing timeonly.

In general, stand mixers of the prior art have permitted the user tolock the head in the up and/or down position or to remove the mixer headfrom the stand, but not perform all three functions. Locking the mixerhead in the up position is desirable because it prevents the head fromfalling back into the bowl. For purposes of carrying the mixer by thehandle, it is desirable to be able to lock the mixer head in the downposition. Furthermore, locking the mixer head in the down positionalleviates bouncing by the mixer head in heavy dough. Removing the mixerhead completely from the stand may often be desirable for individualswishing to use the mixer as a hand mixer rather than a stand mixer.

Other problems inherent in stand mixers is the tendency for water, milk,batter, and other ingredients and liquids to collect in the base of theturntable and cause the bottom of the mixer bowl to stick to the bottomof the turntable, rendering removal of the bowl problematic.

SUMMARY OF THE INVENTION

The present invention solves one or more of the above-referencedproblems of the prior art by providing a whipper design which includesno center bar, thereby eliminating the “dough creep” phenomenon of theprior art. The whippers include increased thickness in the whipperblades, which surprisingly results in no deterioration of mixerperformance.

In another embodiment of the invention, a turntable locator is providedwhich enables the user to adjust the stand mixer to accommodatedifferent bowl sizes without removing the turntable. A slide lever ispreferably employed to position the turntable in two or more positions.

In yet another preferred embodiment of the invention, an improved mixerhead locking feature is provided which locks the mixing head in the downposition, thereby preventing the mixer head from bouncing when the mixeris mixing heavy dough. The feature also allows the mixer head to belocked in the up position for added convenience, and further allows themixer head to be removed completely from the stand to serve as a handmixer.

In yet another preferred embodiment of the invention, the turntableincludes a snap lock feature which eliminates the problem of theturntable sticking to the bottom of the bowl when the bowl is removedfrom the turntable.

In yet another preferred embodiment of the invention, the stand mixerincludes an electrical speed control circuit for providing a temporaryincremental power burst to the motor of the mixer.

These and other objects and advantages of the present invention willbecome more readily apparent from the following detailed description ofthe preferred embodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred stand mixer on the presentinvention.

FIG. 2 is a front elevational view of the stand mixer of FIG. 1.

FIG. 3 is a rear elevational view of the stand mixer of FIG. 1.

FIG. 4 is a left side elevational view of the stand mixer of FIG. 1.

FIG. 5 is a top plan view of the stand mixer of FIG. 1.

FIG. 6 is a perspective phantom line view of the stand mixer of FIG. 1.

FIG. 7 is a side elevation showing the mixer head in a retractedposition.

FIG. 8 is a detail of the turntable slide of a preferred embodiment ofthe present invention.

FIG. 9 is a detail of a preferred snap lock for the turntable of apreferred embodiment of the present invention.

FIG. 10 is a phantom line view of a preferred head lock mechanism of thepresent invention.

FIG. 11 is a perspective view of a preferred band whipper of the presentinvention.

FIG. 12 is a side elevation of the band whipper of FIG. 11.

FIG. 13 is a top plan view of a band for use with the preferred bandwhipper of the present invention.

FIG. 14 is a side elevation view of the band of FIG. 13.

FIG. 15 is a side elevation view of a shaft or spindle for use with theband whipper of FIG. 11.

FIG. 16 is a top plan view of the band whipper of FIG. 11.

FIG. 17 is a bottom plan view of the band whipper of FIG. 11.

FIG. 18 is the electrical circuit diagram of one embodiment of the speedcontrol of the present invention.

FIG. 19 is a table of component values for the circuit diagram shown inFIG. 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is illustrated a preferred stand mixer ofthe present invention, generally 10, comprising a mixer head 12, and abase generally 14, having an upstanding pedestal portion 16 supportingthe mixer head 12. The mixer head 12 in FIG. 1 is shown in the head downor operative position, but the mixer head 12 may also be pivoted into anupended or retracted position by virtue of a pivot point 18 and headlock/release mechanism to be subsequently described. The stand mixerincludes whippers, generally 20, including an outboard whipper 28 and aninboard whipper 30. The whippers 28, 30 mix food and other items in amixer bowl 22, which is supported on a turntable 24, which rotateswithin a base 26 of the stand 14.

In order to perform effective mixing, it is preferable to maintain theoutboard whipper 28 in relatively close proximity to the side of thebowl 22, as is well known in the art. A problem arises when the userdesires to use a differently sized bowl, which requires repositioningthe turntable 24 to accommodate a need to maintain the outboard whipper28 in close proximity with the smaller or larger sized bowl. In thepast, this adjustment has commonly been accomplished by use of spacedholes in the base adapted to receive the axle of the turntable 24. Thisrequires the user to lift the turntable 24 and locate the proper holewhen switching from one size bowl to another. This problem is overcomeby a highly preferred embodiment of the invention which includes aturntable locator feature for moving the turntable 24 from one locationto another on the base 26 without the need to remove the turntable 24from the base 26 and hunt for the appropriate location in the base 26for the turntable. In a highly preferred embodiment the turntablelocator feature includes a slide lever knob 32 which, as seen in FIG. 2,travels within a slot 34 in the base 26. In a preferred embodiment, theturntable position is adjusted simply by sliding the control knob 32 inthe slot 34.

Referring now to FIG. 5, there is illustrated the knob 32 which engagesa lever 36 which pivots about a pivot 38 in the base 26.

As illustrated in FIG. 6, the base 26 includes a slot 40 through whichan axle 42 of the turntable 24 passes. Preferably, this slot 40 is asemicircular curve, the center of which corresponds to the pivot point38. The slot may also be arcuate, i.e., elliptical, or even straight,depending on the contour of the mixer base 26, the width of the slot,and the positioning desired for the turntable 24.

The lever 36 preferably includes ridges 44 (also seen in FIG. 9) whichprovides added strength to the lever and are generally formed by metalstamping procedures. These ridges 44 preferably ride on a pair ofperpendicular ridges 46 in a base plate 48 on the underside of the base26. These ridges cooperate to provide contact points for sliding thelever 44 and for biasing the lever in the appropriate turntablepositions as will subsequently be described.

Referring now to FIG. 8, the lever 36 is retained in the desiredposition by one or more detents 50 in the base 26. In order to relocatethe turntable, the user depresses the lever 36 by pressing down on thecontrol knob 32 in order to overcome the biasing force of the lowerridge 46 on the upper ridge 44, which allows the user to slide the lever36 across the slot 34 until it reaches another detent 50 which allowsthe lever 36 to be retained in the new position. While only two detentes50 are shown in FIG. 8, it would, of course, be possible to includeadditional detentes 50 for more than two bowl sizes. The axle 42 of theturntable 24 may be standard, passing through a hole in the axle 36, ormay be of a snap lock type of a highly preferred embodiment of thepresent invention, described subsequently.

Referring now to FIG. 9, there is illustrated a snap lock mechanism of apreferred embodiment of the invention. In this embodiment, the turntablesnaps into place within the base of the mixer, eliminating the tendencyfor the turntable to stick to a bowl and be inadvertently removed whenthe bowl is removed from the mixer. In this embodiment, the turntable 24includes a series of snaps 60 extend downwardly from the underside 62 ofthe turntable 24. In the embodiment illustrated in FIG. 9, the snaps 60extend through an opening 63 in the lever 36 previously described. Inanother preferred embodiment, the turntable snaps may extend through ahole in the base 26. In this embodiment, the lever 36 is not employed,and the turntable passes through holes in the base itself.

In the embodiment shown in FIG. 9, the snaps 60 also extend through theslot 40 in the base. In a preferred embodiment to the invention, thereare three snaps 60, preferably equally spaced. The snaps 60 may performintegral with the axle 42, or may be attached to the underside of theturntable 62 and separate from the axle 42. Generally, the axle 42remains stationary allowing the lower platter 24 a to remain stationarywith respect to the upper platter 24 b of the turntable which preferablyrides on a bearing allowing the upper platter 24 b to turn with respectto the lower platter 24 a. In addition to the use of snaps 60, it isalso possible to use other snap fit mechanisms, such as an annular ringwhich can be molded directly into a cylindrical shaft extendingdownwardly from the axle 42 and be snap fit into a corresponding groovein either the bottom of the stand 26 or in the lever 36. Also, it wouldbe possible to have an axle and/or snaps extend upwardly from the base26 and/or turntable 36 in order to receive a complimentary opening inthe base 62 of the lower platter 24 a.

As illustrated, the snaps 60 preferably have an inclined surface 70which urges the snap 60 inwardly as it passes through the opening 63 inthe lever 36. Another surface 72 which may also be a straight incline,but may also be a curved surface, is contoured to retain the clip 60 andhence the turntable 24 within the base 26. This same surface 70 is alsocontoured to allow the user to overcome the retention forces of the clip60 by applying a predetermined pulling force sufficient to ensure thatthe turntable 24 is not removed unless it is intended to be removed bythe user.

Turning now to FIGS. 7 and 10 there is illustrated yet another preferredembodiment of the invention comprising an improved headlock mechanism.The improved headlock mechanism comprises a locking pin generally 80which carries a locking flange 82 which is governed by two fork members84, 86 attached to a button 88. The locking flange may be a groove inthe locking pin 80, a projection, a nut, or any other point ofengagement between the locking pin 80 and the fork members 84, 86. Whiletwo fork members 84, 86 are illustrated, only one could be used as well.

The locking pin 80 is biased upwardly by a spring 90, the spring beingcompressed between a washer or nut 92 and a stationary guide plate 93anchored to the pedestal. The locking pin 80 in its normal position isbiased upwardly into a recess 94 contained within the mixer head,thereby precluding the mixer head from being pivoted rearwardly. Inorder to disengage the mixer head and pivot same in a rearwardorientation, the button 88 which may be a momentary switch type, iscompressed and held downwardly, which acts upon the forks 84, 86 whichin turn drive the locking flange 82 downwardly, thereby driving thelocking pin 80 downwardly through a hole in the guide plate 93 and outof the recess 94, enabling the user to rotate the mixer head 12rearwardly about the pivot point generally 18, as illustrated in FIG. 7.As an alternative, the button 88 may engage a detent or other momentaryholding device to hold the button in its down position.

Once the mixer head 12 is fully rotated rearwardly, the lock pin 80 canbe released by releasing the button 88, thereby engaging another recess95 in the housing of the mixer head 12 and thereby locking the head 12in the upright position as illustrated in FIG. 7.

Because the locking pin 80 is slideably received within the recess 94,it does not prevent the mixer head 12 from being removed vertically fromthe stand. The mechanism, generally 100, for removing the head 12 fromthe stand may be conventional, such as that currently used on theMixmaster® Model 2360 Stand Mixer sold by Sunbeam Products, Inc.,Hattiesburg, Miss. Such a mechanism generally includes a latch/springclip 101 actuated by a release button 102 at the rear of the stand,which clip 101 engages a horizontal pivot pin 104 riding in a yoke 105in the pedestal and passing through a flange 106 in the mixer head. Thepivot pin 104 provides the point of engagement for the spring clip 101,thereby retaining the mixer head 12 on the pedestal 16, and also allowsthe mixer head 12 to pivot about the curvilinear pivot point 18 definedby the mixer head 12 and pedestal 16. Thus, while the locking pin 80precludes the mixer head while in its upward or downward position fromshifting positions, the fact it is slideably received in the recess ofthe mixer head allows the mixer head to be removed from the stand.

Of course, it would be feasible to provide recesses in addition torecesses 94 and 95 in the mixer head in order to allow locking the headin intermediate positions. Alternatively, only one of the recesses 94 or95 could be provided. Also, rather than using a spring 90, it would befeasible to employ a slide mechanism with a lock or detent for retainingthe locking pin 80 in its upward position within the mixer head recess94 or 95. The lock or detent would require the user to use sufficientforce to overcome the lock or detent to retract the locking pin 80.

The stand mixer of the present invention preferably includes a powerburst button 11 (FIG. 1) for substantially immediately providing atemporary incremental power burst to the motor of the mixer so long asbutton 11 is depressed. In one embodiment, the stand mixer includestwelve established speeds, the lowest speed (1) corresponding to a motorspeed of approximately 300 rpm, and the highest speed (12) correspondingto a motor speed of approximately 1000 rpm. All of the speeds in thisembodiment are approximately 58 rpm apart. In the preferred embodiment,pushing power burst button 11 causes the motor speed to be increased byapproximately 100 rpm regardless of the established speed setting, thustemporarily boosting the motor speed to a speed equivalent toapproximately two established speeds thereabove. It should be noted thatthe present invention can be implemented in a mixer having any number ofmotor speeds and corresponding rpm values, and can be modified toprovide boosts of speed of any desired magnitude or rpm increase.

FIG. 18 shows the electrical circuit diagram of one embodiment of thespeed control of the present invention. The circuit structure andcomponent values (See FIG. 19) are meant to be for illustrative purposesonly, it being understood that the present invention can be implementedin virtually any conventional speed control circuit for a mixer. In FIG.18, the motor speed is controlled by the firing angle of triac TH1 whichis controlled by output pin 4 of integrated circuit U1. Input pin 11 toU1 is a voltage “speed set” input determined by the voltage divider ofR14, R50, R13 and potentiometer R31. Output pin 10 of U1 provides avoltage that is directly related to the motor speed because U1 includesa frequency to voltage converter which converts the frequency input fromthe tach at input pin 8 to a DC voltage at output pin 10. The frequencyat input pin 8 can be derived by hall effect or coil magnetic pick-upmethods, or any other method known to one of ordinary skill in the art.

U1 will increase the voltage to the motor, via output pin 4, based onthe pin 11 input voltage until the voltage at output pin 10 is equal tothe pin 11 input voltage. If the pin 10 voltage is higher than the pin11 voltage, U1 will decrease the motor speed until the two voltages areequal.

When power burst button 11 is depressed (shown as a normally opencontact in FIG. 18), resister R50 is shorted out, thus increasing the“speed set” voltage input to pin 11 of U1 via the operation of thevoltage divider network. This, in turn, causes the motor speed to beincreased as discussed above. Resistor R50, although indicated as a 10Kohm resister, may be sized to cause a voltage change equal to anydesired burst speed change.

Although the invention has been described in detail with reference tospecific examples and preferred embodiments and illustrations, it is tobe understood that the full scope of the invention is defined by thefollowing claims, as fairly interpreted, including all equivalentsthereof.

We claim:
 1. A mixer comprising: a housing; a motor disposed within saidhousing, said motor adapted for connection to one or more whippers; aspeed control circuit for operating said motor at one of a plurality ofestablished, user-selectable speeds; and a button coupled with saidspeed control circuit which, when depressed by the user of said mixer,causes the speed of said motor to increase by a predetermined incrementfrom one of said plurality of established user-selectable speeds, untilsaid button is released, wherein said predetermined increment isapproximately equivalent to twice the difference in speed between twoadjacent established speeds.
 2. The mixer of claim 1 wherein saidpredetermined increment is adjustable.
 3. The mixer of claim 1 whereinsaid speed control circuit generates a first voltage representative ofthe sensed speed of said motor and a second voltage representative ofthe user-selected speed, and produces a signal for controlling saidmotor based on said first and said second voltages.
 4. The mixer ofclaim 3 wherein said second voltage is generated by a potentiometerinterconnected with a plurality of resistors and wherein said button isconnected across one of said plurality of resistors.
 5. A speed controlcircuit for the motor of a mixer comprising: a first portion forgenerating a first voltage, said first voltage representing auser-selected speed; a second portion for generating a second voltage,said second voltage representing the sensed speed of said motor; a thirdportion for producing a signal for controlling the speed of said motorbased on said first and said second voltages; and a button coupled withsaid third portion which, when depressed by the user of said mixer,causes the speed of said motor to increase by a predetermined incrementfrom said user-selected speed until said button is released.
 6. Thespeed control circuit of claim 5 wherein said predetermined increment isadjustable.
 7. The speed control circuit of claim 5 wherein saidpredetermined increment is approximately equivalent to twice thedifference in speed between two adjacent established speeds.
 8. Thespeed control circuit of claim 6 where said second portion of said speedcontrol circuit includes a tachometer coupled to a frequency to voltageconverter.
 9. The speed control circuit of claim 5 where said secondportion of said speed control circuit includes a Hall effect sensorcoupled to a frequency to voltage converter.
 10. The speed control ofclaim 5 wherein said second portion of said speed control circuitcomprises a potentiometer interconnected with a plurality of resistorsand wherein said button is connected across one of said plurality ofresistors.
 11. The speed control circuit of claim 5 where said circuitfor producing a signal for controlling the speed of said motor includesan integrated circuit for producing a gating signal, and a triacresponsive to said gating signal for conducting current through saidmotor.
 12. A combination comprising: a motor; a circuit for operatingsaid motor at one of a plurality of established, user-selectable speeds;and a button coupled with said circuit which, when depressed by a user,causes the speed of said motor to increase by a predetermined incrementfrom said one of a plurality of established user-selectable speeds,until said button is released, wherein said predetermined increment isadjustable.
 13. The combination of claim 12 wherein said predeterminedincrement is approximately equivalent to twice the difference in speedbetween two adjacent established speeds.
 14. A circuit for controllingthe speed of a motor comprising: means for selecting a speed; means foroperating said motor at said selected speed; and means, when activatedby a user, for causing the speed of said motor to increase by apredetermined increment above said selected speed, wherein saidpredetermined increment is adjustable.